Multidecadal Seesaw in Hadley Circulation Strength Between the Two Hemispheres Caused by the Atlantic Multidecadal Variability
Multidecadal Seesaw in Hadley Circulation Strength Between the Two Hemispheres Caused by the Atlantic Multidecadal Variability
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DOI：
10.3389/feart.2020.580457
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
Yusen Liu;Zhanqiu Gong;Cheng Sun;Jianping Li;Lin Wang
中科院分区：
文献类型：
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作者：
Yusen Liu;Zhanqiu Gong;Cheng Sun;Jianping Li;Lin Wang
历史上Hadley环流强度的年代际变化对全球和区域气候具有重要意义。然而，在两个半球的HC强度之间的关系仍然不清楚。在这项研究中，我们确定了一个半球间的跷跷板在年度HC强度在几十年的时间尺度。这种跷跷板模式在物理上对应于每年HC上升分支的纬向运动，导致一个半球的HC加强，另一个半球的HC减弱。HC强度的跷跷板强烈相关的热带陆面降水在几十年的时间尺度，特别是季风陆地地区。进一步的分析将HC强度的跷跷板与大西洋年代际变率（AMV）联系起来。一套大西洋起搏器实验成功地再现了几十年的HC强度的跷跷板和它的关系，AMV。与AMV正位相相关的北方半球SST增暖导致HC上升分支北移，南半球HC增强，而北方半球HC减弱。北大西洋SST强迫HC之间的耦合的海气模式和独立的大气模式的变化的比较表明，一个重要的和不可忽视的作用的SST足迹的AMV在印度洋-太平洋盆地。AMV及其印度洋-太平洋SST足迹对北方半球SST变化的贡献相当，它们控制着HC上升分支的移动，从而控制着HC强度的南北摇摆。
Multidecadal variations in Hadley circulation (HC) strength have been observed during the historical period, which have significant implications for global and regional climate. However, the relationship between HC intensities in the two hemispheres remains unclear. In this study, we identify an interhemispheric seesaw in the annual HC strength at multidecadal timescales. This seesaw pattern physically corresponds to the meridional movement of the ascending branch of annual HC, leading to strengthened HC in one hemisphere and weakened HC in the other. The HC strength seesaw strongly correlates with the tropical land surface precipitation at multidecadal timescales, particularly for the monsoonal land regions. Further analyses link the HC strength seesaw to the Atlantic multidecadal variability (AMV). A suite of Atlantic Pacemaker experiments successfully reproduces the multidecadal HC strength seesaw and its relation to the AMV. The Northern Hemisphere SST warming associated with the positive AMV phase induces a northward shift of the upward branch of HC, and the Southern Hemispheric HC is strengthened in contrast to the weakened Northern Hemispheric HC. Comparisons of the North Atlantic SST forced HC changes between the coupled air–sea model and stand-alone atmospheric model suggest an important and non-negligible role of the SST footprint of AMV over the Indo-Pacific basins. The AMV and its Indo-Pacific SST footprint make a comparable contribution to the SST changes in the Northern Hemisphere, which control the movement of the HC ascending branch and thereby the interhemispheric seesaw in HC strength.